"Over time we’ve improved search by deepening our understanding of queries and web pages. The web isn’t merely words—it’s information about things in the real world, and understanding the relationships between real-world entities can help us deliver relevant information more quickly", said Google in a blog post.
Google says that they've basically bought the company for two reasons, the first is to help it understand the way we search for information and the second because Metaweb happens to have a database called Freebase, that's a free and open database of over 12 million things, including movies, books, TV shows, celebrities, locations, companies and more.
Google and Metaweb plan to maintain Freebase as a free and open database for the world, presumably so it can take on Wikipedia with its own offering after previous attempts have fallen on deaf ears.
"With efforts like rich snippets and the search answers feature, we’re just beginning to apply our understanding of the web to make search better", claims Google. Metaweb should help them boost that experience even more.